Various technologies have been utilized to track the position of surgical implements in a patient. Ultrasound and other indirect imaging techniques can display a representation of the surgical implement on a screen. Fiduciary markers that show up on ultrasound images, for instance, have been positioned at known locations on or within the patient. The position of the surgical implement can then be compared against the positions of the fiduciary markers to give an approximated position of the surgical implement relative to the markers.